Bridge device failure fix

[Taylor]

Do you know the angle formed between members A and B?
We can obviously figure it out with a bit of trig, but I don't want to rely on a not-to-scale sketch.

[Brandon_L]

Originally Posted by Taylor

Do you know the angle formed between members A and B?
We can obviously figure it out with a bit of trig, but I don't want to rely on a not-to-scale sketch.

We found it by just placing a piece of the metal we were using from the end of A, then down to our frame, making sure when we rotated it it would clear the bumper. It was a on the spot trial and error type of thing. B will not actually touch your frame. Ours floats an inch or so in front of it. As long as the height of it is equal to or a bit below your frame, so that the bridge gets kicked under into your wheels.

Again, I will try go get measurements when we unbag for our 6 hours which would be this saturday.

[Hebrew]

How fast can you get on the bridge with your two front wheels from when the triangle thing first touches the bridge? (I would like to compare it to the speed of our pneumatic arm)

I see a lot of teams with this having to push against the bridge for quite a while before it comes down enough.

[Brandon_L]

with us, its the same speed your driving pretty much. The lower the angle, the better. The closer you get to 90 degrees the more its like hitting a wall, and more force is needed. my guess is ours came out around 20 degrees and its literally almost the same as just driving forward

[E-Stop]

Most teams are using Window or Van door motors but we ended up with an Andy Mark geared motor from the KoP using a 35 chain with a 4:1 gear ration and it had more then enough torque at orlando and we even pushed from the side and can let robots up from the same side to balance themselves if we are doing the cooperation .

[George C]

Looks a whole lot like what we came up with 6-7 weeks ago. We made ours higher (14") off the floor in case the bridge isn't quite level, used a dogleg to get the Centre of Rotation (about 4" off the floor) lower to keep weight low and put adhesive-backed UHMW on the underside of it. We also left a gap in the bumper so it is much closer to the frame. We found that the weight of the robot with a 14" moment arm stripped the gears in the window motor in our first version so we added a pneumatic latch which engages when it's down. It also helps us get over the bump. When it's up, we can use it to tilt the bridge away from us. It doesn't slow us down much so far.

[mman1506]

Like most, are team cam to GTR with 2 window motors on a arm to lower the bridge, Did nothing. We then took a Cim with a tough box and attached that to the arm, again did nothing.

We are now using a 1 1/2" bore cylinder attached to a arm as a 3rd class lever. We get about 50lbs on the end of are arm. It also has the ability to raise the bridge and lock it in a balanced position. It's working great so far in the Waterloo regional.

[Donut]

We finally got to use our bridge manipulator today and found that you don't actually need all that shallow of an angle to get the bridge down. While I would certainly advocate a design like this if you have the room, we have a wedge that extends out around 7" but down 12" and still works (something like a 50 or 60 degree angle). You need a bit of a running start to make sure the bridge gets down well but we've balanced once in practice today and numerous times on the practice field with this so far.

Of course it may not hold up for an entire regional of beating, but we'll know that at the end of Saturday.

Also for teams throwing something like this on last minute, you don't have to use a motor to drive it if you have no other appendage outside the robot. We have a hinge and bungee cord to flip out the wedge as soon as the robot moves and it hangs out the entire match. Saved us the weight of a motor and the time of getting it hooked up.

[Brandon_L]

Originally Posted by Donut

We finally got to use our bridge manipulator today and found that you don't actually need all that shallow of an angle to get the bridge down. While I would certainly advocate a design like this if you have the room, we have a wedge that extends out around 7" but down 12" and still works (something like a 50 or 60 degree angle). You need a bit of a running start to make sure the bridge gets down well but we've balanced once in practice today and numerous times on the practice field with this so far.

Of course it may not hold up for an entire regional of beating, but we'll know that at the end of Saturday.

Also for teams throwing something like this on last minute, you don't have to use a motor to drive it if you have no other appendage outside the robot. We have a hinge and bungee cord to flip out the wedge as soon as the robot moves and it hangs out the entire match. Saved us the weight of a motor and the time of getting it hooked up.

We found it will work with a larger angle, but it works smoother/doesn't require a head start with a smaller angle.

[nitneylion452]

Originally Posted by Brandon_L

We found it will work with a larger angle, but it works smoother/doesn't require a head start with a smaller angle.

Theoretically, this will work with any angle 0 < x < 90.

[Kevin Sevcik]

We came up with this around week 2. Only mistake was direct driving it with a PG71. Worked fine on the practice bridge, but the real thing would've laughed at it. So we're running on a 256:1 P60. After shearing pins, replacing them with PG71 pins and then shearing sun gears, we put a latch on it. Otherwise it works good. An interesting point is that the angle has relatively little effect on the holding torque necessary, unless your pivot is well above 12".

[beiju]

Our team had that in our first regional, but we still weren't able to lower the bridge. I assume it's lack of torque in our drive train, but I want to get other opinions.

We're using 6-wheel drive, with KOP Traction wheels in the center and omni-wheels for the other four. Each side is driven by one CIM (which I think is our problem) into a CIMple box, and the chains are all 1:1 ratios. Another problem was that a last-minute shooter design change forced us to move the arm to the side, and we couldn't afford the weight of a second arm (connected so as to not violate the one appendage rule) on the other side. We plan to fix both of those problems for our next regional, and I hope that will allow us to easily lower the bridge.